A lab-on-a-chip conventionally comprises a molecular sensor connected to an electronic circuit configured for converting the data relating to the content of a fluid (a liquid or a gas) into electrical form. This data may be the presence or absence of a target molecule in the fluid, for example in the framework of a search for a virus in a sample of blood.
Lab-on-a-chip devices are known that use field-effect transistors, in which a molecular sensor is electrically connected to the gate of a transistor. Thus, the variation in potential induced by the detection of the target molecule of the sensor leads to a variation in the drain current of the transistor.
For example, for a variation in potential VG of 0.3 volts on the gate of a conventional field-effect transistor, the value of the drain current Idrain of the transistor may be multiplied by 105.
The slope factor of a transistor—also known by those skilled in the art under the term “sub-threshold swing”—is a value allowing the characterization of the voltage to be applied to the gate of an MOS transistor in order to make its drain current vary by a decade.
In this example, the slope factor of the transistor is equal to 60 mV/decade.
However, this value is too high for some applications, such as for example the detection of deoxyribonucleic acid (DNA) molecules, which require devices having a slope factor less than 60 mV/decade.
Lab-on-a-chip devices also exist that use advanced technologies, such as for example silicon nano-wires or carbon nanotubes, and which enable the fabrication of transistors having a lower slope factor.
However, the fabrication of devices integrating these technologies requires specific and complex methods, which are not yet suitable for industrialization.